Effects of Solution Flow on the Anodic Dissolution of Copper and Mild Steel

An experimental study of the effects of solution flow on the anodic dissolution of mild steel and copper electrodes has shown that the behavior of the ‘normal’ and ‘abnormal’ metals previously predicted by a theoretical analysis can be attained in practice; providing that spurious flow effects relating to the effects of flow on iR drops across nonpassivating films are eliminated. Flat plate electrodes were used in a rectangular duct with Reynolds numbers in the range 4.2 x 10² to 2.8 x 10⁴. Copper dissolution was flow sensitive in the range 10⁻¹ to 2 x 10² A/m², above which the reaction was charge transfer controlled with Tafel behavior up to 10³ A/m²; the experimental flow effects showing good agreement with the theoretical effects of flow. The overpotentials for iron dissolution showed an effect of flow at current densities > 10² A/m², but this effect was found to relate to flow sensitive iR drops.